Annular barrier

ABSTRACT

The present invention relates to an annular barrier to be expanded in an annulus between a well tubular structure and an inside wall of a borehole downhole. The annular barrier comprises a tubular part for mounting as part of the well tubular structure, an expandable sleeve surrounding the tubular part and having an inner face facing the tubular part, each end of the expandable sleeve being connected with a connection part which is connected with the tubular part, a space between the inner face of the sleeve and the tubular part, and an element arranged in connection with the sleeve, the element having a first part and a second part both of which extend around the inner face, the first part of the element being fastened to the inner face.

FIELD OF THE INVENTION

The present invention relates to an annular barrier to be expanded in anannulus between a well tubular structure and an inside wall of aborehole downhole. The annular barrier comprises a tubular part formounting as part of the well tubular structure, an expandable sleevesurrounding the tubular part and having an inner face facing the tubularpart, each end of the expandable sleeve, the expandable sleeve beingconnected with a connection part which is connected with the tubularpart, a space between the inner face of the sleeve and the tubular part,and an element arranged in connection with the sleeve, the elementhaving a first part and a second part both of which extend around theinner face, the first part of the element being fastened to the innerface.

BACKGROUND ART

In wellbores, annular barriers are used for different purposes, such asfor providing a barrier for flowing between an inner and an outertubular structure or between an inner tubular structure and the innerwall of the borehole. The annular barriers are mounted as part of thewell tubular structure. An annular barrier has an inner wall surroundedby an annular expandable sleeve. The expandable sleeve is typically madeof an elastomeric material, but may also be made of metal. The sleeve isfastened at its ends to the inner wall of the annular barrier.

In order to seal off a zone between an inner and an outer tubularstructure or a well tubular structure and the borehole, a second annularbarrier is used. The first annular barrier is expanded on one side ofthe zone to be sealed off, and the second annular barrier is expanded onthe other side of that zone, and in this way, the zone is sealed off.

The pressure envelope of a well is governed by the burst rating of thetubular and the well hardware etc. used within the well construction. Insome circumstances, the expandable sleeve of an annular barrier may beexpanded by increasing the pressure within the well, which is the mostcost efficient way of expanding the sleeve. The burst rating of a welldefines the maximum pressure that can be applied to the well forexpansion of the sleeve, and it is desirable to minimise the expansionpressure required for expanding the sleeve to minimise the exposure ofthe well to the expansion pressure.

When expanded, annular barriers may be subjected to a continuouspressure or a periodic high pressure from the outside, either in theform of hydraulic pressure within the well environment or in the form offormation pressure. In some circumstances, such pressure may cause theannular barrier to collapse, which may have severe consequences for thearea which the barrier is to seal off as the sealing properties are lostdue to the collapse. A similar problem may arise when the expandablesleeve is expanded by means of e.g. a pressurised fluid. If the fluidleaks from the sleeve, the back pressure may fade, and the sleeve itselfmay thus collapse.

The ability of the expanded sleeve of an annular barrier to withstandthe collapse pressure is thus affected by many variables, such asstrength of material, wall thickness, surface area exposed to thecollapse pressure, temperature, well fluids, etc.

A collapse rating currently achievable of the expanded sleeve withincertain well environments is insufficient for all well applications.Thus, it is desirable to increase the collapse rating to enable annularbarriers to be used in all wells, specifically in wells that experiencea high drawdown pressure during production and depletion. The collapserating may be increased by increasing the wall thickness or the strengthof the material; however, this would increase the expansion pressure,which as mentioned is not desirable.

It is thus desirable to provide a solution wherein the collapse ratingof expanded sleeves is increased.

SUMMARY OF THE INVENTION

It is an object of the present invention to wholly or partly overcomethe above disadvantages and drawbacks of the prior art. Morespecifically, it is an object to provide an improved annular barrierwith an increased collapse rating of the expandable sleeve.

A further object of the present invention is to provide an annularbarrier having an increased collapse rating without increasing thestrength of the material and/or wall thickness of the sleeve.

An additional object of the present invention is to provide an annularbarrier having a higher collapse rating for the same strength inmaterial and the same wall thickness of the expandable sleeve, and/orthe same collapse rating for a lesser strength in material or a lesserwall thickness of the expandable sleeve, enabling a lower expansionpressure to be used.

The above objects, together with numerous other objects, advantages, andfeatures, which will become evident from the below description, areaccomplished by a solution in accordance with the present invention byan annular barrier to be expanded in an annulus between a well tubularstructure and an inside wall of a borehole downhole, comprising

-   -   a tubular part for mounting as part of the well tubular        structure,    -   an expandable sleeve surrounding the tubular part and having an        inner face facing the tubular part, each end of the expandable        sleeve being connected with a connection part which is connected        with the tubular part,    -   a space between the inner face of the sleeve and the tubular        part, and    -   an element arranged in connection with the sleeve, the element        having a first part and a second part both of which extend        around the inner face, the first part of the element being        fastened to the inner face,

wherein the second part projects into the space from the first part.

When the sleeve is expanded, the second part projects substantiallyradially out into the space, or at an angle of up to a 45°. In theunexpanded state of the sleeve, the second part abuts the inner face ofthe sleeve extending from the first part and the element issubstantially unbent in relation to the first part. Thus, the secondpart projects substantially axially along the inner face of the sleevewith only a small gap between the inner face of the sleeve and thesecond part.

The collapse rating of the expandable sleeve is thus increased withoutincreasing the strength of the material, the wall thickness of theexpandable sleeve or the overall diameter of the annular barrier.Furthermore, by the present invention, the expansion pressure necessaryto expand the expandable sleeve will not be increased or may even belowered.

The first part of the element, which is fastened to the inner face ofthe sleeve, will follow the sleeve outwards during expansion of thesleeve, the diameter of the first part thus being increased. The secondpart of the element is not fastened to the inner face of the sleeve.When the sleeve is expanded, the second part will follow the first partoutwards in the area where they are connected, but not in its other end.The other end of the second part will project inwards towards thetubular part and thus extend substantially radially inward from thesleeve. The second part of the element will thus project inwards at anangle different from the first part.

That the second part projects into the space from the first part is tobe understood thus that, in the unexpanded state of the sleeve, thesecond part projects from first part at an angle of 0°-15°.

In the expanded state of the sleeve, both the first and second parts ofthe element will add additional strength to expanded sleeve as well as ahigh resistance to collapse. Furthermore, in this state, the second partof the element will function as an internal frame structure of thesleeve having a momentum of resistance in a direction substantiallyperpendicular to the sleeve which is higher than the momentum ofresistance of the first part.

In addition, the sections of the expanded sleeve which are fastened tothe first part of the element will have a reduced outer diameter,resulting in a corrugated expanded sleeve. The corrugations will beannular and strengthen the expanded sleeve even further.

As a consequence, the annular barrier according to invention is able towithstand a higher collapse pressure than prior art annular barriers andwill thus also have enhanced sealing capabilities.

In an embodiment, the second part may have an angle in relation to thefirst part before the expandable sleeve is expanded, and the anglechanges during expansion of the expandable sleeve.

Furthermore, the angle prior to expansion may be 0-20°, preferably 0-5°.

In addition, the angle after expansion may be 45-120°, preferably45-100°, more preferably 50-90°.

Moreover, the second part may be arranged for free movement in the spaceand projects inwards in the space during expansion of the sleeve.

Additionally, the second part may be free and unrestrained of the innerface.

Also, the second part may be movable and able to extend radially inwardstowards the tubular part during expansion of the sleeve.

Furthermore, the second part may form an angle of at least 45° inrelation to the first part during expansion of the sleeve.

In an embodiment, the sleeve after expansion may have two incliningparts and an intermediate non-inclining part when seen in cross-sectionalong a longitudinal extension of the sleeve, and the element may bearranged on the part of the sleeve which is non-inclining.

Moreover, the element may be made of a material able to maintain itsshape after being bent, such as metal.

Additionally, the element may be made of metal, such as steel orstainless steel.

Also, the expandable sleeve may have an outer face onto which at leastone sealing element is arranged opposite the first part of the element.

In one embodiment of the annular barrier according to the presentinvention, the element may extend along an entire inner periphery of thesleeve, e.g. as a ring, providing an interior support structure in theexpanded state of the sleeve all around the inner periphery.

A plurality of elements may be arranged in connection with the sleeve.These elements are distributed with an even or uneven distance betweenthem along a longitudinal direction of the sleeve and extend along theperiphery. They may be positioned in areas of the expandable sleevewhich require more strength than other areas, as these areas are exposedto higher collapse pressure than other areas.

The plurality of elements may be arranged in connection with the sleeveand have a mutual distance between them, all connected to thenon-inclining part of the sleeve.

Furthermore, the sealing elements may have a tapering or triangularcross-sectional shape.

In one embodiment, the element may extend in a longitudinal direction aswell as along the periphery of the sleeve, thereby creating a helicalpath along the inner face of the sleeve seen in the longitudinaldirection of the sleeve.

In addition, the element may comprise a third part which is free andunrestrained of the inner face and arranged opposite the second part sothat the first part is arranged between the third and second parts.

Furthermore, both the second and the third part of the element may beadapted to change their angle in relation to the first part duringexpansion of the expandable sleeve.

Advantageously, the second and third parts are arranged on each side ofthe first part so that the element a substantially U-shaped or C-shapedcross-sectional configuration in the expanded state of the sleeve, andthus providing an interior support frame structure for the expandedsleeve.

Furthermore, the second and/or the third part of the element may have anangle in an expanded state of the sleeve in relation to the inner facebeing larger than 5°.

The first part may be fastened wholly or partly to the inner face or anouter face of the sleeve. In one embodiment, the first part may befastened to the inner face at the transition between the first andsecond/third parts or along an entire width of the first part so thatthe second and third parts, respectively, are free in relation to theinner sleeve.

Moreover, the second part and/or third part of the element may functionas a frame structure for the expanded sleeve.

The element may have a V-shaped, a U-shaped, a C-shaped, or an L-shapedcross-sectional configuration when the sleeve is expanded.

The first part may be welded, glued, bolted, or riveted to the innerface.

In one embodiment, the expandable sleeve may be made of metal or acomposite. In another embodiment, it may be made of polymers, such as anelastomeric material, silicone, or natural or syntactic rubber.

The element may also be made of metal or polymers.

In one embodiment, the first part may have a width between 0.005 m and0.30 m, preferably between 0.01 m and 0.10 m and more preferably between0.01 m and 0.05 m. The second part may have a width of between 0.01 mand 0.30 m, preferably between 0.01 m and 0.1 m, more preferably between0.01 m and 0.05 m.

The expandable sleeve may be capable of expanding to an at least 10%larger diameter, preferably an at least 15% larger diameter, morepreferably an at least 30% larger diameter than that of an unexpandedsleeve and it may have a wall thickness which is thinner than a lengthof the expandable sleeve, the thickness preferably being less than 25%of its length, more preferably less than 15% of its length, and evenmore preferably less than 10% of its length.

In one embodiment, the expandable sleeve may have a varying thicknessalong the periphery and/or length.

In addition, at least one of the connection part may be slidable inrelation to the tubular part of the annular barrier, and at least onesealing element, such as an O-ring, may be arranged between the slidableconnection part and the tubular part. In one embodiment, more than onesealing element may be arranged between the slidable fastening means andthe tubular part.

At least one of the connection part may be fixedly fastened to thetubular part or be part of the tubular part.

The connection part may have a projecting edge part which projectsoutwards from the tubular part.

In one embodiment of the annular barrier according to the invention, theelement may be substituted for at least one section having an increasedthickness in relation to another section of the sleeve when seen incross-section along a longitudinal extension of the sleeve, causing thesection having the increased thickness to be expanded less than anothersection during expansion of the sleeve is.

Furthermore, the present invention also relates to an annular barrier tobe expanded in an annulus between a well tubular structure and an insidewall of a borehole downhole, comprising:

-   -   a tubular part for mounting as part of the well tubular        structure,    -   an expandable sleeve having a longitudinal extension and        surrounding the tubular part and having an inner face facing the        tubular part, each end of the expandable sleeve being connected        with a connection part which is connected with the tubular part,        and    -   a space between the inner face of the sleeve and the tubular        part, wherein the sleeve when seen in cross-section along its        longitudinal extension has at least one section having an        increased thickness in relation to another section of the sleeve        so that the section having the increased thickness is expanded        less than another section when the sleeve is expanded.

The section having the increased thickness may be circumferential.

Moreover, when expanded, the sleeve may have two inclining parts and anintermediate non-inclining part seen in cross-section, and the sectionhaving the increased thickness may be arranged on the non-inclining partof the sleeve.

The section of the sleeve having an increased thickness may be providedby fastening a ring-shaped part onto the sleeve.

The ring-shaped part may be fastened by welding and, in one embodiment,the ring-shaped part may be fastened to an outer face of the sleeve.

In addition, the section of the sleeve having an increased thickness mayhave two inclining end parts in which the thickness of the sleeveincreases.

The expandable sleeve may have an outer face onto which at least onesealing element is arranged opposite the section of the sleeve having anincreased thickness.

Moreover, at least one sealing element may be arranged adjacent to thesection of the sleeve having an increased thickness, and the section ofthe sleeve having an increased thickness may have projections.

In one embodiment, the sleeve may comprise a plurality of sectionsarranged along the non-inclining part of the sleeve and having a mutualdistance between them.

The sealing elements may have a tapering or triangular cross-sectionalshape.

The invention further relates to an annular barrier system comprising anexpansion means and an annular barrier as described above. The expansionmeans may comprise explosives, pressurised fluid, cement, or acombination thereof.

In another embodiment, the annular barrier system may comprise

-   -   a tubular part having an opening,    -   a first connection part surrounding and connected with the        tubular part,    -   a second connection part surrounding and connected with the        tubular part,    -   an intermediate connection part arranged between the first and        second connection parts,    -   a first expandable sleeve connected with the first connection        part and the intermediate connection part enclosing a first        inner space, and    -   a second expandable sleeve connected with the second connection        part and the intermediate connection part enclosing a second        inner space,

wherein at least the intermediate part and the first connection part areslidably connected with the tubular part.

In one embodiment, the annular barrier system may comprise at least twoannular barriers positioned at a distance from each other along the welltubular structure.

Moreover, the invention finally relates to a downhole system comprisinga well tubular structure and at least one annular barrier as describedabove.

In one embodiment of the downhole system, a plurality of annularbarriers may be positioned at a distance from each other along the welltubular structure.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention and its many advantages will be described in more detailbelow with reference to the accompanying schematic drawings, which forthe purpose of illustration show some non-limiting embodiments and inwhich

FIG. 1 shows a cross-sectional view of an annular barrier in anunexpanded condition,

FIG. 2 shows a cross-sectional view of the annular barrier of FIG. 1 inan expanded condition,

FIG. 3 shows a cross-sectional view of an annular barrier in a directiontransverse to the longitudinal extension of the borehole,

FIG. 4 a shows a cross-sectional view of an element according to theinvention in its unexpanded condition,

FIG. 4 b shows a cross-sectional view of the element of FIG. 4 a in itsexpanded condition,

FIG. 5 a shows a cross-sectional view of another embodiment of theelement in its unexpanded condition,

FIG. 5 b shows a cross-sectional view of the element of FIG. 5 a in itsexpanded condition,

FIG. 6 shows a cross-sectional view of another embodiment of an annularbarrier in an unexpanded condition,

FIG. 7 shows a cross-sectional view of the annular barrier of FIG. 6 inan expanded condition,

FIG. 8 shows an enlarged partial view of FIG. 6,

FIG. 9 shows a cross-sectional view of yet another annular barrier in anunexpanded condition,

FIG. 10 shows a cross-sectional view of the annular barrier of FIG. 9 inan expanded condition,

FIG. 11 shows a cross-sectional view of yet another embodiment of anannular barrier,

FIG. 12 shows a cross-sectional view of yet another embodiment of anannular barrier,

FIG. 13 shows a cross-sectional view of the annular barrier of FIG. 12in an expanded condition,

FIG. 14 shows a cross-sectional view of yet another embodiment of anannular barrier,

FIG. 15 shows a cross-sectional view of the annular barrier of FIG. 14in an expanded condition,

FIG. 16 shows a cross-sectional view of yet another embodiment of anannular barrier,

FIG. 17 shows a cross-sectional view of the annular barrier of FIG. 16in an expanded condition,

FIG. 18 shows a cross-sectional view of yet another embodiment of anannular barrier,

FIG. 19 shows a cross-sectional view of the annular barrier of FIG. 18in an expanded condition,

FIG. 20 shows a cross-sectional view of yet another embodiment of anannular barrier,

FIG. 21 shows a cross-sectional view of the annular barrier of FIG. 20in an expanded condition, and

FIG. 22A-D show a cross-sectional view of other embodiments of anannular barrier.

All the figures are highly schematic and not necessarily to scale, andthey show only those parts which are necessary in order to elucidate theinvention, other parts being omitted or merely suggested.

DETAILED DESCRIPTION OF THE INVENTION

Annular barriers 1 according to the present invention are typicallymounted as part of the well tubular structure string before the welltubular structure 3 is lowered into the borehole downhole. The welltubular structure 3 is constructed by well tubular structure parts puttogether as a long well tubular structure string. Often, the annularbarriers 1 are mounted in between the well tubular structure parts whenmounting the well tubular structure string.

The annular barrier 1 is used for a variety of purposes, all of whichrequire that an expandable sleeve 7 of the annular barrier 1 is expandedso that the sleeve abuts the inside wall 4 of the borehole. The annularbarrier 1 comprises a tubular part 6 which is connected to the welltubular structure 3, as shown in FIG. 1, e.g. by means of a threadconnection 18.

In FIG. 1, the annular barrier 1 is shown in a cross-section along thelongitudinal extension of the annular barrier. The annular barrier 1 isshown in its unexpanded state, i.e. in a relaxed position, from which itis to be expanded in an annulus 2 between a well tubular structure 3 andan inside wall 4 of a borehole 5 downhole. The annular barrier 1comprises a tubular part 6 for mounting as part of the well tubularstructure 3 and an expandable sleeve 7. The expandable sleeve 7surrounds the tubular part 6 and has an inner face 8 facing the tubularpart 6. Each end 9, 10 of the expandable sleeve 7 is fastened in aconnection part 12 in the tubular part 6. The connection part 11 maycomprise any kind of suitable clamping means providing a tight fasteningof the sleeve 7.

As can be seen, a space or cavity 13 is formed between the inner face 8of the sleeve 7 and the tubular part 6. In order to expand theexpandable sleeve 7, pressurised fluid is injected into the cavity 13through an expansion means 19, such as a hole 19 or a valve 19, untilthe expandable sleeve 7 abuts the inside wall 4 of the borehole 5. Thecavity 13 may also be filled with cement or the like in order to expandthe sleeve 7. The expansion means may also be an explosive.

When annular barriers 1 are expanded, they are exposed to a certainpressure. However, the pressure may vary during production. As thepressure may thus increase, the annular barrier 1 must be able towithstand an increased pressure, also called “the collapse pressure”,also in its expanded state, when the outer diameter of the annularbarrier is at its maximum and its wall thickness thus at its minimum. Inorder to withstand such an increased pressure, the expandable sleeve 7may be provided with at least one element 14.

In FIG. 1, the expandable sleeve 7 has three elements 14 arranged spacedapart in the longitudinal direction of the expandable sleeve. Eachelement 14 has a first part 15, a second part 16 and a third part 17,all of which extend around and along the inner face 8 of the expandablesleeve. The second part 16 and the third part 17 are arranged onopposite sides of the first part 15, and the first part is fastened tothe inner face 8. The second and third parts 16, 17 are not directlyfastened to the expandable sleeve 7, but only indirectly via the firstpart 15. Thus, the second and third parts 16, 17 project from the firstpart 15 into the space 13 between the expandable sleeve 7 and thetubular part 6 and are able to move freely in the space during expansionof the expandable sleeve.

In the unexpanded state of the sleeve 7, one side of the second andthird parts 16, 17 abut the inner face 8 of the sleeve extending fromthe first part 15 so that the first, second and third parts form astraight line and the element 14 is substantially unbent in relation tothe first part which is fastened to the sleeve. Thus, the second andthird parts 16, 17 project substantially in the longitudinal extensionand along the inner face 8 of the sleeve with only a small gap betweenthe inner face of the sleeve and the second and third parts. In theexpanded state of the sleeve 7, the second and third parts 16, 17project substantially radially out into the space 13 or at an angle ofbetween 45° and 135° to the sleeve.

In FIG. 2, the annular barrier 1 of FIG. 1 is shown in its expandedstate. The first part 15 of each element 14 is expanded together withthe expandable sleeve 7. However, the second and third parts 16, 17 arenot expanded as much as the element 14, and they are thus bent at anangle in relation to the first part 15. The second and third parts 16,17 project radially inwards in relation to the expandable sleeve 7 andfunction as reinforcement, such as a girder in a building or a hull of aboat. In the expanded condition, the elements 14 prevent the annularbarrier from collapsing when submitted to an increased pressure from theannulus 2 or the borehole wall 4. As can be seen, all three elements 14are positioned at the section of the sleeve 7 which in its expandedstate is substantially straight and not part of the inclining ends ofthe annular barrier 1.The third element is positioned at the middlesection of the annular barrier abutting the borehole wall 4.

FIG. 3 shows a cross-sectional view through an element connected with anannular barrier in a direction transverse to the longitudinal extensionof the borehole. The element 14 is fastened to the inner face 8 of theexpandable sleeve 7 and thus follows the curvature of the expandablesleeve on its inside wall. Both the expandable sleeve 7 and the element14 surround the tubular part 6. The element 14 extends along an entireinner periphery of the sleeve 7, forming a ring or an inner sleeve.

When the expandable sleeve 7 of the annular barrier 1 is expanded, thediameter of the sleeve is expanded from its initial unexpanded diameterto a larger diameter. The expandable sleeve 7 has an outside diameter Dand is capable of expanding to an at least 10% larger diameter,preferably an at least 15% larger diameter, more preferably an at least30% larger diameter than that of an unexpanded sleeve.

Furthermore, the expandable sleeve 7 has a wall thickness t which isthinner than a length L of the expandable sleeve, the thicknesspreferably being less than 25% of the length, more preferably less than15% of the length, and even more preferably less than 10% of the length.

In another embodiment, the element 14 extends both in the longitudinalextension of the expandable sleeve 7 and along the periphery of thesleeve, creating a helical path along the inner face 8 of the sleeveseen in the longitudinal direction of the sleeve.

In the embodiment shown in FIG. 1, the first part 15 is completelyfastened to the inner face 8. However, the first part 15 may also beonly partly fastened to the inner face 8. When the sleeve 7 is expanded,the second part 16 and the third part 17 of the element 14 function as aframe structure for the expanded sleeve due to the U-shapedcross-section of the expanded element.

The element 14 may have any suitable cross-sectional shape in theexpanded state of the sleeve 7. In addition to the U-shape, a V-shapemay thus be imagined, or an L-shape if the element 14 only has a firstand a second part 16, 16.

When the first part 15 is fastened to the inner face 8, the second andthird parts 16, 17, respectively, are able to move freely in relation tothe sleeve 7. The first part 15 of the element may be fastened at thetransition between the first and second/third parts or along an entirewidth of the first part. The first part may be fastened in any suitableway, e.g. welded, glued, bolted or riveted to the inner face 8.

The element 14 may be made of any suitable material and/or a compositeable to expand and subsequently add strength to the expanded element.Examples of suitable materials are metal or polymers.

The expandable sleeve 7 of the annular barrier 1 may be made of metal orpolymers, such as an elastomeric material, silicone, or natural orsyntactic rubber.

Providing the annular barrier 1 with a valve 19 makes it possible to useother fluids than cement, such as the fluid present in the well or seawater, for expanding the expandable sleeve 7 of the annular barrier.

As can be seen, the expandable sleeve 7 is a thin-walled tubularstructure, the ends 9, 10 of which have been inserted into theconnection part 12. Subsequently, the connection part 12 has beenembossed, changing the design of the fastening means and the ends 9, 10of the expandable sleeve and thereby mechanically fastening them inrelation to one another. In order to seal the connection between theexpandable sleeve 7 and the connection part 12, a sealing element 20 maybe arranged between them.

In FIG. 4 a, an element 14 to be connected with the inner face 8 of theexpandable sleeve 7 is shown in cross-section. The element 14 comprisesa first part 15, a second part 16 and a third part 17. According to theinvention, the first part 15 is fastened to the inner face (not shown),whereas the second and third parts 16, 17 are not fastened and are thusfree in relation to the inner face. During expansion of the expandablesleeve 7, the first part 15 of the element 14 will follow the expansionof the sleeve outwards, increasing the diameter of the first part. Thesecond and third parts 16, 17 will follow the first part 15 in the areawhere they are connected, but not in their other ends. The second andthird parts 16, 17 will thus project inwards at an angle from the firstpart 15, which is shown in FIG. 4 b.

In FIG. 5 a, another embodiment of an element 14 is shown incross-section. In this embodiment, the element 14 comprises a first part15 and a second part 16, the second part having an angle in relation tothe first part in a non-expanded state. As described above, the secondpart 16 will project inwards during expansion of the expandable sleeve7, as shown in FIG. 5 b. In this case, where the second part 16 alreadyin the non-expanded state projects inwards, less expansion force isrequired.

Furthermore, the second part 16 and/or the third part 17 may be arrangedat an angle in relation to the first part 15, away from the inner face8. The second part 16 and/or the third part 17 may comprise anadditional flange arranged at the end furthest away from the first part15, providing these parts with extra strength, thus increasing thecollapse rating of the expanded sleeve 7 even further.

In FIG. 6, another annular barrier 1 is shown, wherein the expandablesleeve 7 of the annular barrier 1 has been laminated with an additionalmaterial 30 in predetermined areas, i.e. in those areas where theexpanded sleeve 7 is exposed to maximum hydraulic pressure.Advantageously, this additional material 30 may be stronger than thematerial of which the rest of the expandable sleeve is made.

Normally, a stronger material will be less ductile. When only laminatingthe expandable sleeve 7 with the additional stronger material 30 incertain areas, an increased collapse rating of the expandable sleevemay, however, be achieved without affecting the expansion properties ofsleeve.

Lamination of the expandable sleeve 7 may be performed in many differentways, e.g. by laser welding of dissimilar metals, cladding, etc.

When a stronger but less ductile material 30 is laminated onto theexpandable sleeve 7, the material of which is not quite as strong, butmore ductile, the result is an expandable sleeve which is stillsufficiently ductile, but the collapse rating of which is increased. Inits expanded state, the sleeve 7 will thus be able to withstand a higherpressure close to or at the point of lamination.

When the expandable sleeve 7 is laminated with an additional material 30in certain areas, the wall thickness of the sleeve is increased in theseareas. This increase in the wall thickness is easier deduced from FIG.8.

In FIG. 7, a cross-sectional view of the annular barrier 1 of FIG. 6 inits expanded state is shown. In this embodiment, the additional material30 with which the sleeve has been laminated provides an increasedcollapse rating of the expandable sleeve and thus of the annular barrier1.

In another aspect, the expandable sleeve may comprise at least twodifferent materials, one having a higher strength and thereby lowerductility than the other material having a lower strength but higherductility. Hereby, the expandable sleeve may comprise the materialhaving the higher strength in areas of the sleeve which are exerted forhigh hydraulic collapse pressure, when the sleeve is expanded, andcomprise the material having a lower strength in the remaining areas ofthe sleeve. When the expandable sleeve comprise a material of higherstrength with low ductility in certain areas and having a material oflower strength but high ductility in the remaining areas, the expandablesleeve maintains sufficient ductility whilst the lower strengthexpandable sleeve material gains in collapse resistance. Once expanded,the overall effect being an expandable sleeve with a higher collapseresistance close to or at the areas where the sleeve comprises thematerial of higher strength.

In FIG. 9 another aspect is shown, wherein both ends 9, 10 of theexpandable sleeve 7 are fixed to the well tubular structure 3. Normally,when the expandable sleeve 7 expands diametrically outwards, theincrease in diameter of the expandable sleeve will cause the length ofthe sleeve to shrink and the thickness of the wall of the sleeve tobecome somewhat decreased.

If two ends 9, 10 of the sleeve are fixed and no other changes are madeto the design of prior art annular barriers, the degree to which thewall thickness would have to be decreased to achieve high diametricalexpansion would be increased, leading to a lower collapse rating andpossible burst of material.

In an additional aspect, the expandable sleeve 7 is provided with aseries of circumferential corrugations 40 along the length of theexpandable sleeve. The series of circumferential corrugations 40 enablesan increase in the length of the expandable sleeve 7 between the twofixed ends 9, 10 without increasing the distance between the two fixedends.

After forming the above-mentioned corrugations 40, the expandable sleeve7 may be subjected to some kind of treatment, e.g. heat treatment, toreturn the material of the sleeve to its original metallurgicalcondition.

During expansion of the expandable sleeve 7, the corrugations 40 arestraightened out, providing the additional material necessary for largediametrical expansion (e.g. 40% in diameter) without overly decreasingthe wall thickness and while still keeping the two ends 9, 10 fixed.This is shown in FIG. 10. Preventing excessive decrease in wallthickness will maintain the collapse rating of the expandable sleeve 7,which will be appreciated by the skilled person.

Fixing the two ends 9, 10 while at the same time achieving maximumdiametrical expansion capability (e.g. 40% in diameter) is particularlyadvantageous in that it eliminates moving parts and thus the expensiveand risky high pressure seals required for these moving parts. This isof particular importance in regard to high temperatures or corrosivewell environments, e.g. Acid, H₂S, etc.

In another aspect, the wall thickness of the expandable sleeve along thelength of the sleeve may be profiled, which will allow control of theexpansion in relation to where wall thinning would occur of theexpandable sleeve. The profiling may be made to the expandable sleevevia laminating of the same or different materials to the surface of theexpansion sleeve or could be via machining or rolling the expandablesleeve to varying thicknesses.

When the expansion is controlled through varying the wall thickness, itis possible to vary the collapse rating at certain points along thelength of the expandable sleeve.

Another aspect of the annular barrier 1 is shown in FIG. 11. In one endof the annular barrier 1, the connection part 12 in which the sleeve 7is fastened is slidably connected with the tubular part 6 (illustratedby an arrow) via slidable fastening means 22. When the expandable sleeve7 is expanded in a direction transverse to the longitudinal direction ofthe annular barrier 1, the sleeve will, as mentioned above, tend toshorten in its longitudinal direction, if possible. When having slidablefastening means 22, the length of the sleeve 7 may be reduced, making itpossible to expand the sleeve even further, since the sleeve is notstretched as much as when it is fixedly connected with the tubular part6.

However, having slidable fastening means 22 increases the risk of theseals 20 becoming leaky over time. A bellow 21 is therefore fastened tothe slidable fastening means 22 and fixedly fastened in the connectionpart 12. In this way, the connection parts 12 can be fixedly connectedto the tubular part 6. The expandable sleeve 7 is firmly fixed to thefirst connection part 12 and to the slidable fastening means 22, and thebellow 21 is firmly fixed to the slidable fastening means 22 and thesecond connection part 12. Accordingly, the connection parts 12, theexpandable sleeve 7, the slidable fastening means 22 and the bellow 21together form a tight connection preventing well fluid from entering thetubular structure 3.

The incorporation of two ends fixed with maximum diametrical expansioncapability is considered beneficial in that this would eliminate movingparts, and no expensive and risky high pressure seals within thesemoving parts are needed. This is of particular importance whenconsidering high temperature or corrosive well environments, e.g. Acid,H₂S etc.

When the annular barrier 1 has slidable fastening means 22 between thesleeve 7 and the tubular part 6, the expansion capability of the sleeveis increased by up to 100% compared to an annular barrier without suchslidable fastening means.

In FIGS. 12 and 13, the annular barrier 1 has six elements 14 of whichthree are arranged in one end of the sleeve 7 and three are arranged inthe other. In FIG. 12, the sleeve 7 has not yet been expanded, but inFIG. 13, it is shown in its expanded condition. The sleeve 7 has twoinclining parts 32 and one intermediate non-inclining part 33. Theelements 14 are situated so that none of them are fastened in the partof the sleeve 7 inclining after expansion, but they are all positionedat a substantially straight non-inclining part 33 of the sleeve afterexpansion. The first part 15 of the elements 14 is welded to the innerface 8 of the sleeve 7 forming a welded connection 42, and the secondand third parts 16, 17 of the element 14 are not fastened to the sleeve,but are free to move during expansion.

When placed near the inclining part, as shown in FIG. 13, the sixelements 14 increase the collapse pressure even further than when placedcloser to the middle of the sleeve 7.

In FIG. 14, the sleeve 7 has an outer face 34 having two sealingelements 35 opposite the first part 15 of each element 14. Whenexpanded, as shown in FIG. 15, the sealing elements 35 fit into thegroove 36 created by the element due to the increased thickness of thesleeve 7 and the first part 15 of the element.

The sealing elements 35 have an outer corrugated face for increasing thesealing ability. The sealing elements 35 have a triangularcross-sectional shape so as to fit the groove 36 occurring in the sleeve7 during expansion. The sealing elements 35 are made of an elastomer orthe like material having a sealing ability and being flexible.

In FIGS. 16 and 17, the outer surface of the tubular part 6 of theannular barrier 1 has a serrated configuration, and the elements havecorresponding points 37 at their ends matching the serrated surface ofthe tubular part. When the sleeve 7 is expanded, as shown in FIG. 17,the points of the elements are fixated in the serrations 38 of thetubular part, and the ends of the elements are maintained in thisposition, thereby strengthening the collapse pressure.

The elements are arranged in the non-inclining part of the sleeve 7, andthe second and third parts 16, 17 of each element are long enough thereach the outer face of the tubular part 6 so as to fit into theserrations 38 and be fastened in these serrations. The tubular part 6has several serrations so to fit several expansion diameters of thesleeve 7. By having several serrations, the annular barrier 1 is ablefit even if the sleeve 7 is expanded in an uneven manner, causing a partof the sleeve to be expanded less than another part.

Furthermore, the connection parts 12 of the annular barrier 1 of FIGS.16 and 17 are made of a different material than the expandable sleeve 7.The connection parts 12 are welded with the sleeve 7 when manufacturingthe annular barrier 1.

By collapse pressure is meant the pressure by which an outside pressurecan collapse an expanded sleeve 7. The higher the collapse pressure, thehigher the pressure from the formation and the annulus the expandedsleeve 7 is able to withstand before collapsing.

In FIG. 18, a double annular barrier is shown. The annular barrier 1 hastwo end connection parts 12 and a middle connection part. The twoexpandable sleeves 7 are fastened to one end connection part and themiddle part, as shown in FIG. 18. The middle connection part is slidableas is one of the end connection parts 12. The other end connection part12 is firmly fastened to the tubular part 6. The annular barrier 1 hastwo openings for injection of pressured fluid for expansion of thesleeves 7.

FIG. 19 shows another embodiment of a double annular barrier having onlyone opening for injection of pressured fluid for expansion of thesleeves 7. The annular barrier 1 has two cavities, and the middleconnection part 12 has a channel 40 fluidly connecting the two cavitiesso that fluid for expanding the cavity having the opening is able toflow through the channel to expand the other sleeve 7 as well.

In order to increase the collapse pressure, a circumferential section 41of the intermediate non-inclining part 33 may have an increasedthickness when seen in a cross-sectional view along the longitudinalextension of the sleeve 7 as shown in FIG. 20. When expanding the sleeve7, this section 41 of the sleeve is expanded less than another sectionalong the non-inclining part 33, resulting in a corrugated shape of thesleeve.

In order to increase the thickness of a section 41 of the sleeve 7,additional material is applied onto the inner face 8 of the sleeve, e.g.by adding welded material onto the inner face.

In another embodiment, the thickness of the section of the sleeve 7 isincreased by fastening a ring-shaped part onto the sleeve. Thering-shaped part is the element 14 and is fastened onto the innersurface by means of welding or the like suitable fastening process.

As shown in FIG. 20, the section 41 of the sleeve 7 having an increasedthickness has two inclining end parts in which the thickness of thesleeve increases. Thus, the added material may be applied to the innerand/or outer face of the sleeve, increasing the thickness of the endparts of the section towards the centre of the section. In addition, thefastened ring-shaped part 14 is chamfered after the fastening process.

Along the non-inclining part 33, the sleeve 7 may also have an increasedthickness on its outside and the sleeve may also have a ring-shaped partfastened to the outer face 34 of the sleeve.

On the outer face 34 of the expandable sleeve, sealing elements 35 arearranged opposite the sections of the sleeve having an increasedthickness. When the sleeve 7 is expanded as shown in FIG. 21, thesealing elements 35 fill up the gap occurring during expansion. In orderto fit the gap better, the sealing elements 35 have a tapering ortriangular cross-sectional shape.

Also as shown in FIG. 20, a connection 39 is positioned between thesleeve 7 and the connection part 12. The connection 39 may e.g. beprovided by means of welding.

In FIG. 22A, the sleeve 7 of the annular barrier 1 has three elements 14fastened on the outer face 34 of the sleeve, increasing the thickness ofthe sleeve wall.

The element is a ring fastened by means of welding. During expansion ofthe sleeve 7, the elements 14 arranged on the outer face 34 prevents thesleeve from expanding freely in these section. Consequently, the sleeve7 is expanded to a lesser extent in these sections than in othersections and the cross-sectional shape of the sleeve is a corrugated.

In FIG. 22B, the three elements 14 of FIG. 22A have been welded alongeach of their circumferential edges. The welded material 43 is appliedin the transition between the element 14 and the sleeve 7 and providesthe element with a tapering cross-sectional shape resulting in a morecontrolled curvature of the sleeve. The welded material 43 may also bechosen as being more corrosion-resistant or providing another property.During expansion of the sleeve 7, the elements 14 arranged on the outerface 34 prevents the sleeve from expanding freely in these section.Consequently, the sleeve 7 is expanded to a lesser extent in thesesections than in other sections and the cross-sectional shape of thesleeve is a corrugated.

In FIG. 22C, the sleeve 7 has three sections 41 with an increased wallthickness. The thickness of the sleeve wall is increasing outwards in aradial direction, providing the sleeve with projections extendingcircumferential outwards. In this embodiment, the elements 14 arrangedon the outer face 34 thus also prevents the sleeve from expanding freelyin these section. Consequently, the sleeve 7 is expanded to a lesserextent in these sections than in other sections and the cross-sectionalshape of the sleeve is a corrugated.

In FIG. 22D, the sections 41 having an increased thickness are providedwith projections 44 in the form of peaking edges or several spikes inorder to obtain a metal-to-metal seal when the sleeve 7 is expanded. Onone or both sides of the peaking edges or spikes, O-rings may bearranged around the sleeve 7 to provide a better seal.

The corrugated cross-sectional shape which the sleeve 7 obtains duringexpansion serves to increase the collapse pressure is substantially.This corrugated cross-sectional shape is obtained by providing elements14 on the inner and/or outer face of the sleeve 7, or by providing thesleeve with an increased thickness in certain sections 41.

The sleeve 7 has a longitudinal extension along its centre axis, shownin FIGS. 2, 6, 7, and 9-22B as a dotted line. The cross-sectional viewsof these figures are rotational symmetric around the centre axis.

The present invention also relates to an annular barrier systemcomprising an annular barrier 1 as described above. The annular barriersystem moreover comprises an expansion tool for expanding the expandablesleeve 7 of the annular barrier 1. The tool expands the expandablesleeve 7 by applying pressurised fluid through a passage 19 in thetubular part 6 into the space 13 between the expandable sleeve and thetubular part.

The expansion tool may comprise an isolation device for isolating afirst section outside the passage or valve 19 between an outside wall ofthe tool and the inside wall of the well tubular structure 3. Thepressurised fluid is obtained by increasing the pressure of the fluid inthe isolation device. When a section of the well tubular structure 3outside the passage 19 of the tubular part 6 is isolated, it is notnecessary to pressurise the fluid in the entire well tubular structurejust as no additional plug is needed, as is the case in prior artsolutions. When the fluid has been injected into the cavity 13, thepassage or valve 19 is closed.

In the event that the tool cannot move forward in the well tubularstructure 3, the tool may comprise a downhole tractor, such as a WellTractor®.

The tool may also use coiled tubing for expanding the expandable sleeve7 of an annular barrier 1 or of two annular barriers at the same time. Atool with coiled tubing can pressurise the fluid in the well tubularstructure 3 without having to isolate a section of the well tubularstructure; however, the tool may need to plug the well tubular structurefurther down the borehole from the two annular barrier or barriers 1 tobe operated. The annular barrier system of the present invention mayalso employ a drill pipe or a wireline tool to expand the sleeve 7.

In one embodiment, the tool comprises a reservoir containing thepressurised fluid, e.g. when the fluid used for expanding the sleeve 6is cement, gas or a two-component compound.

An annular barrier 1 may also be called a packer or the like expandablemeans. The well tubular structure 3 can be the production tubing orcasing or a similar kind of tubing downhole in a well or a borehole. Theannular barrier 1 can be used both in between the inner productiontubing and an outer tubing in the borehole or between a tubing and theinner wall of the borehole. A well may have several kinds of tubing, andthe annular barrier 1 of the present invention can be mounted for use inall of them.

The valve 19 may be any kind of valve capable of controlling flow, suchas a ball valve, butterfly valve, choke valve, check valve or non-returnvalve, diaphragm valve, expansion valve, gate valve, globe valve, knifevalve, needle valve, piston valve, pinch valve or plug valve.

The expandable tubular metal sleeve 7 may be a cold-drawn or hot-drawntubular structure.

The fluid used for expanding the expandable sleeve 7 may be any kind ofwell fluid present in the borehole surrounding the tool and/or the welltubular structure 3. Also, the fluid may be cement, gas, water,polymers, or a two-component compound, such as powder or particlesmixing or reacting with a binding or hardening agent. Part of the fluid,such as the hardening agent, may be present in the cavity 13 beforeinjecting a subsequent fluid into the cavity.

Although the invention has been described in the above in connectionwith preferred embodiments of the invention, it will be evident for aperson skilled in the art that several modifications are conceivablewithout departing from the invention as defined by the following claims.

1. An annular barrier to be expanded in an annulus between a welltubular structure and an inside wall of a borehole downhole, comprisinga tubular part for mounting as part of the well tubular structure, anexpandable sleeve surrounding the tubular part and having an inner facefacing the tubular part, each end of the expandable sleeve beingconnected with a connection part which is connected with the tubularpart, a space between the inner face of the sleeve and the tubular part,and an element arranged in connection with the sleeve, the elementhaving a first part and a second part both of which extend around theinner face, the first part of the element being fastened to the innerface, wherein the second part projects into the space from the firstpart.
 2. An annular barrier according to claim 1, wherein the sleeveafter expansion has two inclining parts and an intermediatenon-inclining part when seen in cross-section along a longitudinalextension of the sleeve, and the element is arranged on the part of thesleeve which is non-inclining.
 3. An annular barrier according to claim1, wherein the element is made of a material able to maintain its shapeafter being bent, such as metal.
 4. An annular barrier according toclaim 1, wherein the expandable sleeve has an outer face onto which atleast one sealing element is arranged opposite the first part of theelement.
 5. An annular barrier according to claim 2, wherein a pluralityof elements are arranged in connection with the sleeve and have a mutualdistance between them, all connected to the non-inclining part of thesleeve.
 6. An annular barrier according to claim 1, wherein the elementcomprises a third part which is free and unrestrained of the inner faceand arranged opposite the second part so that the first part is arrangedbetween the third and second parts.
 7. An annular barrier according toclaim 1, wherein the second and/or the third part of the element has anangle in an expanded state of the sleeve in relation to the inner facebeing larger than 5°.
 8. An annular barrier according to claim 1,wherein the first part is fastened wholly or partly to the inner face oran outer face of the sleeve.
 9. An annular barrier according to claim 1,wherein the element has a V-shaped, a U-shaped, a C-shaped, or anL-shaped cross-sectional configuration when the sleeve is expanded. 10.An annular barrier according to claim 1, wherein the element issubstituted for at least one section having an increased thickness inrelation to another section of the sleeve when seen in cross-sectionalong a longitudinal extension of the sleeve, causing the section havingthe increased thickness to be expanded less than another section duringexpansion of the sleeve is.
 11. An annular barrier according to claim10, wherein the section of the sleeve having an increased thickness isprovided by fastening a ring-shaped part onto the sleeve.
 12. An annularbarrier according to claim 10, wherein the section of the sleeve havingan increased thickness has two inclining end parts in which thethickness of the sleeve increases.
 13. An annular barrier according toclaim 10, wherein the expandable sleeve has an outer face onto which atleast one sealing element is arranged opposite the section of the sleevehaving an increased thickness.
 14. An annular barrier according to claim4, wherein the sealing elements have a tapering or triangularcross-sectional shape.
 15. An annular barrier system comprising anexpansion means and an annular barrier according to claim
 1. 16. Anannular barrier system according to claim 15, wherein the expansionmeans comprises explosives, pressurised fluid, cement, or a combinationthereof.
 17. A annular barrier system comprising: a tubular part havingan opening, a first connection part surrounding and connected with thetubular part, a second connection part surrounding and connected withthe tubular part, an intermediate connection part arranged between thefirst and second connection parts, a first expandable sleeve connectedwith the first connection part and the intermediate connection partenclosing a first inner space, and a second expandable sleeve connectedwith the second connection part and the intermediate connection partenclosing a second inner space, wherein at least the intermediate partand the first connection part are slidably connected with the tubularpart.
 18. A downhole system comprising a well tubular structure and atleast one annular barrier according to claim
 1. 19. A downhole systemaccording to claim 18, wherein a plurality of annular barriers arepositioned at a distance from each other along the well tubularstructure.